Ingredients
Equipment
Method
Caramelize the onions
- Heat the olive oil and butter in a 10-inch skillet over medium heat.
- Add the onions, salt, and pepper, and cook over medium-low heat, stirring occasionally, for 30 to 35 minutes, until very soft and golden brown.
- Stir in the thyme and balsamic vinegar and cook for 1 minute, until the vinegar has mostly evaporated.
Assemble and bake
- Heat the oven to 400°F.
- Line a 13x18-inch baking sheet with parchment paper.
- Unfold the puff pastry on the baking sheet and gently roll it into an approximately 10-inch square.
- Score a 1/2-inch border without cutting through.
- Prick the center all over with a fork.
- Spread the goat cheese over the center of the pastry.
- Top evenly with the onions.
- Beat the egg with the water.
- Brush the egg mixture over the pastry border.
- Bake for 20 to 25 minutes, until the pastry is puffed and deep golden brown and the bottom is crisp.
- Let the tart rest on the baking sheet for 5 minutes.
- Slice and serve.
Notes
For the best texture, make sure the onions are very soft and golden brown before adding them to the pastry. Refrigerate leftovers for up to 3 days; freezing is not recommended because the pastry can lose its crispness. Use gluten-free puff pastry for a gluten-free option, if available.
